Aerogels of natural polysaccharides possess both biocharacteristics of polysaccharides, such as good biological compatibility and cell or enzyme-controlled degradability, and aerogel characteristics, such as very high porosity and specific surface areas that makes them highly attractive in drug delivery. Biodegradable alginate aerogels were synthesized via a sol-gel process. In the present work two methods of ionic cross-linking were used to prepare alginate hydrogels as monoliths and spheres, which can be further easily converted to high surface area aerogels. The aerogels obtained were further used as drug carriers. We investigated the effect of process parameters, such as starting concentration and viscosity of alginate solution, on synthesis products and on model drug (nicotinic acid) release. The results indicate that by using the internal setting cross-linking method for obtaining monolithic aerogels nicotinic acid was released in a more controlled manner. The aerogels thus obtained also exhibited smaller volume shrinkage than the ones described in other publications. However, with increasing alginate concentration in both types of synthesis more compact and cross-linked aerogels were formed.
We have studied the solubility of SC CO2 in the biodegradable polymers poly(L-lactide) (PLLA), poly(lactide-co-glycolide) (50:50) (PLGA) and poly(ε-caprolactone) (PCL). The solubility data at different temperatures (308–373 K) and pressures (10–30 MPa) were determined experimentally for each polymer by using a magnetic suspension balance. The results showed that SC CO2 solubility is high in all studied polymers, increases with increasing pressure and decreases with increasing temperature. Starting from experimental data, two mathematical models, Sanchez–Lacombe equation of state (SL EOS) and the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT), were used to predict the phase equilibrium and the necessary binary interaction parameters were determined from correlation with experimental data.
The application of polyethylenes in the powder coating industry as film formers is highly interesting. Due to their excellent chemical and physical properties they can be used for anticorrosion protection. In present work properties of polyethylenes (PE) of various densities (low density PE - LDPE and high density PE- HDPE) under the pressure of CO2 have been researched. The aim was to investigate the phase equilibria of PE of various density in presence of CO2 in dependence of pressure and temperature. The phase transitions of polymers at atmospheric pressure were determined by differential scanning calorimetry (DSC). Moreover, phase transitions of polymers under pressure of gas were measured by using an optical high pressure cell. Measurements of phase transition were performed in pressure range from (1–400 bar). The solubility of CO2 in polymers was determined at different pressures and temperatures by magnetic suspension balance (MSB) and these data were used for estimating the binary diffusion coefficients.